Dimorphotheca sinuata -- Arizona

Dimorphotheca sinuata is an annual wildflower native to Namibia and South Africa that has been widely commercialized as an ornamental for its attractive and colorful flowers (Dave's Garden, 2021). It has escaped cultivation and often can be found naturalized in open and disturbed sites (Rojas-Sandoval, 2020). The plant is adapted to arid environments, and is known to naturalize in Arizona (Martin, 2021), (Kinsey, 2021). It is found in 18 counties in California, chiefly in southern California (Calflora, 2021).

The plant is adapted to arid environments, and is known to naturalize in Arizona (Martin, 2021), (Kinsey, 2021), this matches with the native habitat in southern Africa, as well as introduced occurrences in southern California (Calflora, 2021) and Australia (GBIF, 2021).

CABI Invasive Species Compendium notes Dimorphotheca sinuata has been naturalized in many parts of the world, It is listed as invasive only in the Dominican Republic but it is also regarded as an emerging environmental weed in Australia and California (Rojas-Sandoval, 2020). CABI differentiates between "naturalized" and "invasive" which lends weight to the statement of this species as invasive. Nevertheless, an occurrence in Dominican Republic is not shown in GBIF (2021), and this reduces the confidence to "Medium".

CABI Invasive Species Compendium notes Dimorphotheca sinuata is listed as invasive only in the Dominican Republic (Rojas-Sandoval, 2020). The Caribbean Region is not a similar climate to southern Africa, and this occurrence is not shown in GBIF (2021) which reduces confidence of this report.

Calflora records Dimorphotheca fruticosa as naturalized in southern California (Calflora, 2021). Dimorphotheca tragus and D. pluvialis are other species of Dimorphotheca native to southern Africa, and shown as occurring in the American Southwest. The latter is also shown as occurring in the matching climate of Australia (GBIF, 2021). However the occurrences of these species appear to be naturalized rather than invasive.

Occurrences shown by GBIF are predominantly in matching climates of the American Southwest and Australia. Other occurrences are scattered in other parts of Africa, North America, and Europe (GBIF, 2021).

There is no information concerning this plant's abilities to compete in non-native situations. Many studies were available describing its competitive abilities intraspecifically, or interspecifically within its native environment (Halvorson & Guertin, 2003). By inference, the small stature and annual habit of the plant render it unlikely to have a smothering effect on plant communities, however it might compete with other annual wildflowers sharing the same winter-growing habit.

No information is available on the plant's potential to support fire. Its small stature and low biomass (Dave's Garden, 2021) do not suggest much potential.

Parts of plant are poisonous if ingested (Dave's Garden, 2021). However this information is not elaborated elsewhere, so the claim is questionable. The small size and annual growth habit of the plant make it unlikely to impact grazing systems.

The plant is a low-growing herbaceous annual, growing to 12 inches tall (Halvorson & Guertin, 2003), too small to form thickets or impediments.

The plant is an herbaceous annual which reproduces by seed. Vegetative propagation is not noted (Dave's Garden, 2021). Being an annual, all vegetative growth will die at the end of the growing season, limiting any capacity for vegetative proliferation.

A capacity for vegetative propagation is not noted (Dave's Garden, 2021). Being an annual, all vegetative growth will die at the end of the growing season, limiting any capacity for vegetative proliferation.

Dimorphotheca sinuata produces dimorphic fruits (two different achenes/seeds). These achenes/seeds are morphologically and anatomically different, with each having different responses to environmental conditions, ensuring species' survival. Seeds tend to drop from the plant as soon as they are mature. Achenes of the disc flowers are winged, having better dispersal mechanisms than achenes of the ray flowers, which are non-winged (Halvorson & Guertin, 2003).

The plant is an annual usually no more than 12 inches tall (Halvorson & Guertin, 2003), with large flowers somewhat limited in number due to the expense of producing them. By inference, one plant is unlikely to produce 1000 seeds.

Seeds of various ages were germinated in laboratory conditions at 59°F (15°C) in germination blotters, germination ranged between 54-73% for seeds less than a year old, 71-84% after 6 years of storage, 71-84% after 11 years, 71-80% after 16 years. Seeds were stored at 41°F (5°C) and at 40% relative humidity (Halvorson & Guertin, 2003). Confidence is rated as "High" but not "Very High" because these were laboratory tests rather than field tests.

The plant is an annual, producing seeds by the end of the growing season within one year (Halvorson & Guertin, 2003).

The Jepson eFlora lists the flowering time Feb--Jun (Keil, 2012), which is greater than a three month period and warrants a yes. However phenology statements such as this in floristic works usually refer to the flowering period of the species across its range, and not the flowering period for an individual plant. The plant is an annual with a single seed production period at the end of the growing season (Halvorson & Guertin, 2003). More information is needed to determine if the flowering period mentioned in the Jepson eFlora reflects seed production for individuals or groups of individuals within a population.

Seeds tend to drop from the plant. Achenes of the disc flowers are winged, having better dispersal mechanisms than achenes of the ray flowers, which are non-winged (Halvorson & Guertin, 2003). The winged seeds are adapted to wind dispersal. There appear to be no adaptations for dispersal by mammals or birds.

Achenes of the disc flowers are winged, having better dispersal mechanisms than achenes of the ray flowers, which are non-winged (Halvorson & Guertin, 2003). The winged seeds are adapted for wind dispersal. However because of the low stature of the plants, by inference it is unlikely these seeds regularly have long-distance dispersal capacity of 100 meters or more.

Dimorphotheca sinuata has been widely commercialized as an ornamental for its attractive and colorful flowers (Dave's Garden, 2021). It has escaped cultivation and often can be found naturalized in open and disturbed sites (Rojas-Sandoval, 2020). It is highly likely to be transported internationally deliberately (Rojas-Sandoval, 2020). The seeds are sold, either pure or within flower seed mixtures, by such high-profile companies as High Country Gardens (2022), True Leaf Market (2022) and Urban Farmer (2022). The Tucson-based company "The Native Seed Company" (2022) sells packets of pure daisy seed. I have interpreted the presence of Dimophotheca seeds in flower seed mixtures as equivalent of contaminated seed, even if their presence is intentional.